This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to German Application No. 200 19 969.2 filed on Nov. 23, 2000, the entire content of which is incorporated herein by reference.
The invention generally relates to a bearing and a bearing arrangement incorporating the bearing. More particularly, the present invention pertains to an antifriction bearing that is designed as a movable bearing and a bearing arrangement in which the antifriction bearing is employed.
For an antifriction bearing of relatively high quality to reliably operate over a long period of time, the antifriction bearing typically has to be installed with a defined play or with a defined initial tension. For this reason, it is known in the art to use an antifriction bearing, for example a cylindrical roller bearing, and to adjust the play or the initial tension by widening the inner raceway to the required extent. This procedure has proven successful for a broad range of applications. However, this procedure has also been shown to sometimes suffer from the drawback that an adjustment is possible only within relatively narrow limits. Additionally, the adjustment causes the inner raceway to be subject to very high mechanical stress.
It is also known in the art to design the geometry of the antifriction bearing in such a way that an adjustment is possible without deforming the inner or the outer raceway. German Patentschrift No. 496 492 proposes an antifriction bearing in which the rollers run between a cylindrical and a conical raceway and are themselves conically shaped. To adjust or readjust the antifriction bearing, the rollers are shifted in the axial direction relative to the conical raceway. An antifriction bearing constructed in this way permits simple and precise adjustment and readjustment, but raises some problems regarding the running properties of the bearing. The conical rolling elements rolling along the cylindrical raceway force a sliding movement between the rolling elements and the cylindrical raceway. This sliding movement can cause the running properties of the antifriction bearing to deteriorate and can result in premature wear.
A need thus exists for an antifriction bearing that permits relatively simple adjustment of the play or the initial tension to thus largely reduce or negate problems such as those associated with known antifriction bearings as mentioned above.
An antifriction bearing includes a first bearing ring and a plurality of rolling elements each having a lateral surface possessing a conical shape, with the rolling elements being positioned between a conical raceway and a cylindrical raceway to roll along the conical raceway and the cylindrical raceway, and with the first bearing ring having a running surface constituting one of the conical raceway and a cylindrical raceway. The lateral surface of each rolling element forms an angle with a center axis of the rolling element that is 3xc2x0 at maximum, and the lateral surface of each rolling element has a convex curvature that is superimposed on the conical shape.
According to one version of the present invention, the conical raceway is formed by the first running surface of the first bearing ring and the cylindrical raceway is formed by the running surface of a second bearing ring or by the running surface of a machine part such as a shaft.
The antifriction bearing according to the invention has the advantage that it affords a relatively precise and easy-to-handle adjustment of the play or the initial tension in the bearing while at the same time possessing excellent running properties. Excellent running properties and very good adjustability of the play or the initial tension can be achieved if the angle formed by the lateral surface of each rolling element and the center axis of the rolling element is between about 0.5 and 1.5 degrees.
It is particularly advantageous to construct the rolling elements so that the curvature of the lateral surface of each rolling element follows a logarithmic profile.
To facilitate lubrication of the antifriction bearing in its installed state, it is advantageous to provide the first bearing ring, whose cross-section increases from a first axial end segment to a second axial end segment, with at least one radial through-bore in the first axial end segment or at least one continuous radial indentation in the end face of the rolling element adjacent to the first axial end segment.
According to another aspect of the invention, an antifriction bearing includes a cage, a plurality of rolling elements arranged in the cage and positioned between a conical raceway and a cylindrical raceway to roll along the cylindrical raceway and the conical raceway, with each rolling element having an outer surface possessing a conical shape. The outer surface of each rolling element forms an angle with a center axis of the rolling element that is 3xc2x0 at maximum, and the outer surface of each rolling element has a convex curvature that is superimposed on the conical shape.
In accordance with another aspect of the invention, an antifriction bearing arrangement includes a first machine element, a second machine element, and an antifriction bearing positioned between the first and second machine elements. The antifriction bearing has a plurality of rolling elements each having opposite end faces and an outer surface possessing a conical shape, with the rolling elements being adapted to roll along a conical raceway and a cylindrical raceway. The lateral surface of each rolling element forms an angle with a center axis of the rolling element that is 3xc2x0 at maximum, and the lateral surface of each rolling element has a convex curvature that is superimposed on the conical shape. In addition, a stop element is provided and has a stop face contacted by the end face of each rolling element.
Advantageously, the stop face is axially movable relative to the antifriction bearing. With the aid of the axial movement of the stop face, a predefined play or a predefined initial tension of the antifriction bearing can be set. In a preferred embodiment, the stop face is convexly curved which, among other things, facilitates the supply of lubricant and/or coolant to the contact area between the stop face and the rolling elements.
The stop element can be made of a non-hardened materials that it possesses a certain degree of elasticity. In addition, to minimize wear of the stop element, the stop element is preferably hardened, especially induction-hardened, in the area of the stop face.
The stop element can be embodied as a nut with an external thread. The nut is preferably equipped with an anti-rotation element in the form of at least one grub screw which interacts with at least one bolt. The stop face can be formed on an axial extension of the nut.